Methacryloxy and/or acryloxy groups are introduced into liquid-crystalline polyorganosiloxanes so that the latter can be crosslinked. This crosslinking can take place, for example, by a free radical or ionic reaction on the ethylenic double bonds of the (meth)acryloxy groups. In order to obtain highly three-dimensionally crosslinked liquid-crystalline polyorganosiloxane, it is desirable to introduce the highest possible content of (meth)acryloxy groups into the polyorganosiloxane. However, if liquid-crystalline polyorganosiloxanes having a high content of (meth)acryloxy groups are prepared, according to U.S. Pat. No. 4,388,453, only hazy and rough films can be produced with these materials after orientation. The use of the non-mesogenic bifunctional monomers mentioned, such as allyl (meth)acrylate, results in materials having a narrow phase range and very poor orientability. Unreacted monomers without (meth)acryloxy groups which cannot be incorporated into the three-dimensional network and impair the properties of the networks remain in the materials.
If liquid-crystalline polyorganosiloxanes having a high content of (meth)acryloxy groups are prepared by the process described in U.S. Pat. No. 5,211,877, films of improved but still unsatisfactory transparency can be produced with these materials. In addition, the expensive use of protective groups is necessary according to U.S. Pat. No. 5,211,877. Complete removal of excess (meth)acrylic acid and/or derivatives thereof cannot be achieved, or can be achieved only with great additional expenditure, in the process described in U.S. Pat. No. 5,211,877, so that the materials obtained cause an intensive odor nuisance and readily polymerize prematurely.